MP Board · Class 12 · Biology · Organisms and PopulationsDiscuss the major abiotic factors that influence the life and distribution of organisms in various biomes. Explain temperature, water, light, and soil in detail.

Introduction to Abiotic Factors\nThe environment of an organism consists of biotic components (living beings) and abiotic components (non-living physical and chemical factors). The regional and local variations in these abiotic factors, coupled with annual variations in precipitation and temperature, lead to the formation of major biomes such as desert, rain forest, tundra, and deciduous forest.

1. Temperature\nTemperature is the most ecologically relevant environmental factor.

• Key Points:
  • Average temperature on land varies seasonally, decreasing progressively from the equator towards the poles and from plains to mountain tops.
  • It ranges from subzero levels in polar areas to >50°C in thermal springs and desert deeps.
  • Temperature affects the kinetics of enzymes, basal metabolism, and other physiological functions of organisms.
  • Organisms can be Eurythermal (tolerant of a wide range of temperatures, e.g., humans) or Stenothermal (restricted to a narrow range of temperatures, e.g., penguins).

2. Water\nWater is essential for life; life on earth originated in water and is unsustainable without it.

• Key Points:
  • Productivity and distribution of plants are heavily dependent on water availability.
  • For aquatic organisms, the quality (chemical composition, pH) and salinity of water become critical.
  • Organisms are divided into Euryhaline (tolerant of wide ranges of salinities) and Stenohaline (restricted to narrow ranges of salinities, e.g., goldfish in fresh water cannot survive in seawater).

3. Light\nSunlight provides energy for photosynthesis, which is the primary source of food for almost all life on Earth.

• Key Points:
  • Many plants depend on sunlight to meet their photoperiodic requirements for flowering.
  • The availability of light on land is closely linked with temperature since the sun is the source for both.
  • Deep in the oceans (>500m), the environment is dark, and benthic organisms do not have access to sunlight.
  • Photoperiodic cues also regulate foraging, reproductive, and migratory activities in many animals.

4. Soil\nThe nature and properties of soil in different places depend on the climate, the weathering process, whether soil is transported or sedimentary, and how soil development occurred.

• Key Points:
  • Soil composition, grain size, and aggregation determine the percolation and water-holding capacity of the soils.
  • Parameters such as pH, mineral composition, and topography determine the benthic and vegetative growth in a given area.
  • In aquatic environments, sediment characteristics often determine the type of benthic animals that can thrive there.